Signs and Portents of Iceland

Icelandic volcanoes are all about long term projections. They do not do things in the short run, before any eruptions you will see either several intrusive episodes like at Eyjafjallajökull, or you will see signs of steadily mounting pressure prior to an eruption.

For some Icelandic volcanoes these two processes goes on for decades, or even several centuries. In a select few volcanoes this process takes from a few years to a few decades. In both cases the processes leaves tracks that we can follow through instrumentation.

For a handful of Icelandic volcanoes we have instrumental records that are beneficial for predicting their near future. These predictable volcanoes are Krafla, Bárdarbunga, Grimsvötn and Eyjafjallajökull. The special case where we do have a record but are still not able to make long term predictions is Hekla, which is a truism I will get back to later in this article.

Even though we lack long term data prior to eruptions for Askja and Katla we do think we can make accurate short term predictions ranging from days to weeks. And since both of these can cause massive problems this is a good thing.

So, without much of a further a due, here is comprehensive list of what these volcanoes are up to now and which ones are close to erupting. I am obviously leaving out the volcanoes that may in the future erupt that we lack good records of.

Askja

Technically not Askja, but nearby Herdubreid is more beautiful.

After a 50 year long deflationary period there are signs that magma has started to slowly accumulate again at root level. No large scale intrusions has so far occurred to the upper magma chamber, nor is there any signs on the GPS-station that magma pooling has reached a level even close to what it was prior to the last eruption. This is currently a volcano that is definitely several years to decades away before an eruption can occur.

Bárdarbunga

Recent field measurements taken by the Icelandic Met Office and the University of Iceland gives at hand that two processes are occurring at the same time, there are both root filling of magma at depths of 15 kilometers and post eruptive deflation in the large magma chamber.

People tend to see the spattering of earthquakes at 0 to 7km as signs of an upcoming eruption, but these earthquakes are caused by subsidy of the caldera “plug” as it lowers and it is an ongoing process that started during the eruption itself. Over time the amount of M3+ earthquakes has steadily dropped and over the next few years Bárdarbunga will become ever more quiescent. It is though good to remember that Bárdarbunga has always been a very noisy volcano.

Current estimate is that Bárdarbunga is anything from 3 years to several decades away from the next eruption.

Grimsvötn

The GPS-station Nunatak.

After the last large eruption in 2011 Grimsvötn went into a period of almost dormancy due to lack of system pressure as a significant amount of magma had been erupted. After a period of 3 years we started to see signs that system pressure was picking up, especially if we look at the Cumulative Seismic Moment (CSM) plot. According to this plot we are about 2 to 3 years away from the next Grimsvötn eruption.

GPS trajectories at Grimsvötn normally support this steady inflation model. During an eruption you get a marked deflation, that post-eruption slowly inflates again at a steady pace, before the process repeats itself. The GPS and CSM curves pretty much used to march on hand in hand.

But, sometimes even the most predictable volcanoes can do things that are a bit out of the ordinary. In Grimsvötns case this has to do with the volcano having 3 distinct magma chambers. Two of them are reaching into the caldera; these are the NW and NE magma chambers. The NE magma chamber has not erupted in instrumented history and it is believed to be both old and severely damaged after a large eruption during the Saksunarvatn Tephra eruptions.

If we instead look at the NW magma chamber we find a true volcanic monster. It is of equal size to Bárdarbunga, but the rate of eruption is several times larger, indicating a higher magma intrusion rate. It stands for all known observed eruptions from Grimsvötn, among them the 1996 eruption of Gjálp that was equal in size to Holuhráun and the 2011 eruption that was even larger. Half of all ash and lava produced in Iceland since 1783 is estimated to have originated from this magma chamber alone. This is what we know as the Grimsvötn volcano proper.

Cumulative Seismic Moment plot courtecy of Iceland Met Office.

So, it should be safe to assume that this is the most likely spot to erupt in Iceland? No, not right now since the signs are not entirely there. Up until the eruption at Holuhráun there were almost no signs of increased pressure on the CSM and the GPS-trajectory flat-lined after only two years. And during the Holuhráun eruption this magma reservoir even showed signs of relaxing as intra-volcanic pressure caused by Bárdarbunga diminished.

Now there are probably some people saying that I have been talking about Grimsvötn being close to an eruption, and also that the CSM and GPS-trajectories are moving nicely in a direction pointing towards an upcoming eruption. And yes, they do and I did.

The problem is just the where part of where the eruption will occur. Let us start with the trusty old CSM plot that so far has not failed us when predicting Grimsvötn. It is a sum of released seismic moment in the form of earthquakes. The bulk of the earthquakes that has started to lift the curve of the plot have not happened inside the caldera or along the usual NW magma chamber radial fissures as they have previously.

Instead the earthquakes have occurred around the Southern magma chamber that resides outside of the caldera under what by some is seen as a twin volcano of Grimsvötn called Háabunga, or at two radial fissures associated with Háabunga. One of the fissures goes towards the Hámarínn Volcano and the other towards the Thordharhyrna Volcano.

So, what does the GPS say? Well, first we need to discuss the location of the GPS station. It is placed on a Núnatak on the southern caldera wall just south of the tip of the NW magma chamber and just north of the southern magma chamber. During a normal eruption it will move about 30cm north and west and drop about 25 centimeters. Then it will steadily move up and to the southeast roughly the same amount before the next eruption occurs. Keep this in mind, because now things will be turned around.

If we look at the GPS we see the regular pattern up until just prior to the Holuhráun eruption with steady up, south and east components. This stalled right prior to the eruption and even reversed a bit due to intra-volcanic pressure drop.

After the eruption we get a rather unprecedented pattern where it looks like two opposing forces are fighting for dominance. There is no sign of the steady nice movement that we have seen between every instrumentally recorded eruption. And around volcanoes new things are pretty much always bad things.

This leads us to the activity of the last two months. In the beginning I wrote it off as ice-buildup or a technical failure. But, as time passed on and as the GPS-movements surpassed any known ice-buildup recorded I got highly intrigued. And since there were no signs of instrumental failure I started to see the figures as possible correct. Also, both the GFUM and GRIM stations gave the same data.

I still waited to see if I could detect any movement from nearby stations that would support the GFUM/GRIM-station data in what is called a teleseism (distant effects from volcanic intrusion). These are normally delayed in time, and so it was here. The detectable signals are small but they are there if you remove seasonal variations and the behavior of the individual volcanoes they belong to (Bárdarbunga, Vonarskard and Hamarínn).

GFUM/GRIM GPS-plot courtesy of Icelandic Met Office.

If we put all of these things together we see a minor intrusion at the northern end of the Háabunga magma chamber pushing GFUM/GRIM stations 40mm north, 30mm west and 90mm up in 2 months time. The high up-component is probably due to the station being between two inflating magma chambers, think of it like two inflating balloons pushing towards each other, anything in between will be lifted upwards at express speed compared to if there was only one balloon.

Before we start talking about Háabunga there is one thing I should point out, it is likely that the intra magma chamber pressure battle will cause the NW magma chamber to erupt again instead. This chamber is after all far more fractured due to regular eruptions and far more prone to failure than the chamber of Háabunga.

Háabunga is potentially bad news since we only know two things about it. The first thing we know is that the magma chamber is equal in size to the NW magma chamber that causes the Grimsvötn eruptions. The second thing we know is that this is the only magma chamber at the Grimsvötn/Háabunga massif that has not gone caldera. Mind you, I am not saying that it will go caldera, not at all.

We do not know how a Háabunga eruption would be, we do not know if it would be massively explosive, or if it would be benign and effusive. We do know that there have been radial eruptions towards Hamarínn and fissure swarm eruptions down towards Thordharhyrna, but there all of our knowledge ends.

We also do not know how large the signs would be before an eruption occurs, logically we know that since it has not erupted for at least 1 000 years it is likely to give off pretty noticeable earthquake swarms prior to erupting, regardless if it will erupt upwards or via a fissure since neither the top of the chamber nor the sides should be fractured.

Right now things are hanging up in the air, either we get a “traditional” eruption at Grimsvötn or we get an unknown eruption at Háabunga. Either way I think that Háabunga is here to stay as a potential eruptive place and that it is only a question of time before it will erupt.

The latest computer model I have made is giving a potential point of eruption at anything between 3 months and 3 years. I will follow this particular volcano even more diligently in the near future.

Hekla

Eruptions in Hekla are caused by two things. Steady pulling apart of the Heklugjá fissure as Iceland drifts apart and steady state intrusion of magma from the MOHO. As the tension and pressure becomes too much for the overburden to contain the fissure opens up and we have an eruption.

The constant pulling apart of the thin hot crust on top of the fissure produces very little seismic signals between and during eruptions, and since the intruding magma barely contains more volume than the volume the separation creates there are few pressure increase related earthquakes.

Neither does Hekla produce large changes in the GPS since the fissure pulls apart at almost the same speed that the magma intrudes. The only thing that really moves is the top of Hekla that steadily drops between eruptions due to the weight of the edifice pushing the entire volcano downwards at a rapid pace through the thin hot crust above the fissure. Still there is evidence of inflation, but visible as East and West spread mated with no down-component.

Hekla is since 2011 the most instrumented volcano on the face of the planet, and this makes it possible to see things that were not possible to see during prior eruptions. Even the 2000 eruption occurred almost in the dark. But now things happens in the light of glowing instruments in the dark of the night.

Hekla earthquake plot from 2011. Courtesy of Icelandic Met Office.

Now we can see quite a few minute earthquakes occurring, and here is what is a real breakthrough. We can see a definite trend that follows the pattern of the other well known seismically quiet volcano on Iceland (Grimsvötn).

If we look at the new plot that the Icelandic Met Office has started to produce we see that there is a steady and marked trend towards more earthquakes at Hekla of a size larger than M0.8, and we can also see that the curve of increase is logarithmic (same as at Grimsvötn).

Since we do not have a complete pre-eruptive sequence for the 2000 eruption we can’t predict accurately when an eruption will occur, we can just say that we are now rapidly closing in on one.

Let us now play a bit with this curve and pull it out into the future, in 3 years time we will have more than one earthquake larger than M0.8 every week. And we do know that this did not happen prior to the 2000 eruption, so it is probable that an eruption will occur prior to that.

So, by using the traditional model for Grimsvötn upon Hekla and the known record during the last couple of years prior to the 2000 eruption and then applying all the new equipment it is possible for the first time ever to give a medium term prediction for Hekla. And that ends up with being anything between 1 hour and 3 years with a 70 percent confidence. I should point out that there is not a lack of instrumentation that gives the low confidence number, it is the lack of instrumented record.

Katla

As almost everyone has noticed Katla has been a bit festive lately. There have been repeated earthquake swarms of unusual magnitude sizes. Only problem here is that all earthquakes have been shallow indicating movement of hydrothermal water and not intrusions of magma. This could though over time change, but there are currently no signs of an eruption being close by, at least not more signs than before the seismic hubbub started.

The deeper earthquakes have all occurred at the Gódabunga magma intrusion. The magma here originates from a separate magma conduit outside of Katla and may constitute a formative volcano between Katla and Eyjafjallajökull. The area has for the last 25 years been the most seismically active region in Iceland and the level of activity is currently low for this volcanic feature.

The question about Katla is more why it is not erupting, because this is an unusually long interlude for this particular volcano. My personal opinion is that the repeated intrusions into Gódabunga has somehow siphoned off magma from the MOHO that otherwise should have gone into Katla, if I am correct this will probably have consequences for Katla in the long term.

Krafla

Well, I did mention this volcano as one that we have a good record of and that we should be able to predict prior to an eruption. Only problem is that this particular volcano works on such a timeframe that we will most likely not have any use for that information in a couple of centuries. So if you wish for a volcano prediction for Krafla you will have to dig me up in a couple of centuries.

Conclusion

Krafla steaming.

In the end not much and everything has changed in Iceland over the last year. Yes, it is still the extended system of Grimsvötn that is the most likely to erupt soon. But, it is likely that it will be an intriguing new part of the Massif that will be erupting.

At Hekla we have learned that we now can say that it is likely to erupt soon with a greater confidence, but we already knew that it was probably to erupt soon anyway. The really new part for Hekla is actually that we now with great confidence can say when it is not going to erupt, and that is brand spanking new.

And for those who see a lot of earthquakes at Katla and Bárdarbunga it is time to start looking closely at where the earthquakes occur, and what the reasons behind them are. Otherwise you will miss out on all the wonderful trends that are real out there and that are proven to be indicators of upcoming eruptions.

Some of you may have noticed that I omitted to mention the strainmeters located at Hekla. There is a reason for this. Lately there has been an almost religious belief about those spreading in various sites, a belief that I fully intend to debunk in my next article.

Nice article. Fully agree with most volcanoes, albeit I am a bit skeptical on Katla, Hekla and Askja for different reasons.

Hekla. The reasoning makes much sense, to predict an eruption within 3 years, but this assumes that most likely Hekla will keep same behavior it did since 1947 (eruptions every 10-20 years). But Hekla erupted with longer repose periods before that. Most detected quakes would have been instrumentally invisible prior to 2011. I still have no clue what will happen with Hekla but I like your reasoning.

Katla. First: We did see some deep quakes at Katla, of 10km or deeper. Few yes, but they did happen over the past few months. Second: it is thought that Katla main chamber is very shallow so deep swarms would not make sense. GPS rises every year, so it also does not give us any further clue. I still think Katla could have a run-up of 1-3 months before it does erupt.

Askja. This volcano erupted somewhat “frequently” since 1875, until 1961. Importantly, Askja has been having deep swarms since several years, plus GPS changes. I think this is one of the likeliest volcanoes to erupt in Iceland, as it is one of the few with reliable deep swarms. The run-up to an eruption could last only a few weeks, ending up with a typical small fissure efusive eruption. I think Askja could very likely erupt within the next 10-15 years, due to the frequent deep intrusions. So far magma intrusions have been confined to deeper parts of the crust but that could change rapidly.

Hekla
Yes, a volcano can change its behavior, but it is normally going to do so in the same general direction that it is changing already. And the longterm trend since 1000AD is towards more frequent eruptions. There are no current signs that it will be changing back from the high rate of eruptions that we have seen since 1947.
Second of all, I was talking about earthquakes larger than M0.8 and we do have a complete record for those since 1998 if I remember correctly.
It may though interest you that I actually factored in a longer repose period as one of the uncertainties in the confidence percentage.

Katla
I am aware of the small number of deeper earthquakes at Katla, but there are not more of those than we have seen since the first instruments was put in place. If Katla had become more restless we should see a marked increase in those, and there has been none.

Askja
Yes, you are correct that there has been small earthquake swarms at Askja. Only problem I see is that those swarms are fairly small compared to other volcanoes in the vicinity. Just compare with Herdubreid or Kistufell and you should understand my point here.
In regards of those nice deep earthquakes, here is a conundrum. In all other volcanoes where we have seen them in the vicinity we have seen inflation soon after, but for some reason not at Askja. And that leads us to the GPS. I do not understand where people get the inflation idea from since there is no sign of it at all on the GPSes.
Instead there is an instrumental record of deflation since the Krafla Fires, and that probably started after the last eruption in the sixties at Askja.
Here is the GPS at Askja showing exactly this:

The (long-term trend of) deflation of Askja is very interesting indeed.
As it started when the Krafla fires were ongoing, almost as the magma under the crust was being drained that direction.

I came up with my own theory – perhaps you want to look at it – though I have not confirmed it in any way:

That at a certain period of at most a few years a hotspot pulse of a large pool of magma occurs deep under Bardarbunga. I supposed that this has happened at least around the early 1700s, then around 1861 and in recent years (2010-2015). Making a period of about 150 years or so.

As this happens the first response is to see an increase rate of eruptions in Vatnajokull and some big ones. Then magma migrates north and southwestwards (albeit very deep in the upper mantle), and then intrudes the volcanoes in those directions, finally affecting reaching years down the road the volcanoes further in the north of Iceland (like Krafla) and further southwest (like Westman Islands or Reykjanes).

There is at least one study that made me think of this apparently-crazy theory: that the hotspot plume actually was inferred to divide into two plumes one towards the north one towards the southwest (I can try to send you a link of this article if I find it). A third plume division was postulated towards Hofsjokull. All of this occurs of course in the upper mantle, so we would never detected any earthquakes related to this.

What I saw was this:
– an increase in Grimsvotn and Bardarbunga eruptions apparently around 1700, then Krafla erupted in 1720s, together with other Icelandic volcanoes like Kverfjoll and Oraefajokull.
– a first rifting eruption southwest of Bardarbunga in 1861-1864, followed by Askja in 1874-1875, then many frequent eruptions at Grimsvotn. In 1902-1910, Thordarhyma and Bardarbunga erupted, and more Askja eruptions years later. Much later in the century Krafla erupted again circa 1976, together with Tjornes quakes (this was also the time that the Westman Islands erupted). Askja deflated since then and Vatnajokull was very quiet since 1938. Almost as activity spreaded northwards and southwestwards across those several decades. Like a fissure rifting triggering the adjacent further north and further south rifting fissure swarms.
– new pulse of magma occured at Bardarbunga and Grimsvotn early this century, with the new mantle magma detected in the eruptions of 2011 and 2014.

Data is obviously lacking to confirm this.

I would not say that this is a clear pattern in any way. It might just be that I terribly misinterpreted this data. (Also something does not fit into the pattern: the supposed pulse of new magma at Grimsvotn in 1783) (or that early in the millenium, Reykjanes volcanoes were very active at the same time that Vatnajokull volcanoes were very dormant) Things are very complex.

You missed out on there being two pulses in Iceland. Or cycles is a better word.
One is the mantleplume pulses that occur roughly every 120 years. The second is the rifting cycle that comes about every 250ish years.
If you put those two cycles into your theory it makes better sense to what you are writing.

“People tend to see the spattering of earthquakes at 0 to 7km as signs of an upcoming eruption, but these earthquakes are caused by subsidy of the caldera “plug” as it lowers and it is an ongoing process that started during the eruption itself.”

But IMO said back in May:

“The analysis of the earthquake data suggests that the movement on the fault is opposite to what it was during the subsidence period during the Holuhraun eruption. Continuous GPS measurements show movements away from Bárðarbunga, suggesting inflation. Satellite images processed by the University of Iceland show that hydrothermal cauldrons in the ice at the caldera rim have been deepening, which might reflect increasing geothermal activity.”

Carl, I know this has been aired before, but I am puzzled by the KISA GPS plots which seem to show the nunatak it is on rising. Since that nunatak is on the rim of the caldera, presumably your view is that the up movement is distortion of the edifice as the plug descends.

Good one Mike!
I forgot the cauldrons!
But before we get to the cauldrons let me start with the mixed signals. The deep root-filling of magma I mentioned is causing a large area signal of inflation, because there is inflation at depth. This signal is visible over a fairly large part of Iceland.
But nearby signals show that the bottom of the caldera is dropping, which is also evidenced by the downward slip angles of the larger (M3.5+) earthquakes.
As the root-inflation continues the pressure increases in the system and the drop of the plug is slowly diminishing, which is also evident in the drop in frequency of large earthquakes.

Now over to the cauldrons. There is no definite answer to those, but I do think that the standard model is covering them. As seismic activity occurs there is fracturing that creates spaces for magma to move upwards into areas at the sides of the ring fault and even into the plug itself where water resides. This is normal after large eruptions.
In fact, Bárdarbunga is weirdly inactive in regards of hydrothermal activity compared to Katla, Grimsvötn and Kverkfjöll. For such a large volcano there should be a sub-glacial permanent lake, but there is none. This is in a way secondary evidence of the low level intra-caldera activity caused by that thick plug.

Again another of my speculative theories (second one this morning!):
Bardarbunga is following the fate in the future, of Hofsjokull, as the hotspot migrates further east-southeastwards.

Hofsjokull is mostly dead. Once it was the center of the hotspot and it formed this massive volcano, with a massif as large as Bardarbunga if not larger. Hofsjokull is truly massive, a sign of what once was, but now not receiving the large pool of magma anymore. That changed to Bardarbunga.

Bardarbunha has been king for a long time probably. But I think the next king (or queen) will be Grimsvotn. Or in fact it already is. Laki eruptions will become the norm rather than Veidivotn ones. And Grimsvotn erupts much more than Bardarbunga.

With time as the hotspot migrates even further southeast, Oraefajokull will become the new queen and Grimsvotn will slowly die out.

That gets a bit tricky to add up the vectors… and I’m not sure if the data is there to support that. In all the thinking about the hotspot don’t forget the MAR! That side of Iceland is itself migrating to the East-Southeast. So for the hotspot to migrate to the East-Southeast within Iceland it must be moving even faster than the Icelandic crust in order to ‘overtake’ it! Do hotspots really move that fast?

I strongly suspect that the hotspot actually plays a significant role in initiating the rifting process, at least in Iceland. Bardarbunga eruption was an event which supports this theory. I think central volcanoes intrude magma towards the lines of least resistance, which creates rifts parallel to previously existing ones.

In the future, I think Grimsvotn fissure swarm will create the majority of new rifting fissures (part of MAR) along the dead zone and possibly northwards too.

In the far future it might be Oraefajokull to do that. At the moment no rifting occurs towards the west or southwest of Oraefajokull but that could change in the more far future. Laki so far is at the far end of the rifting zone of the MAR called dead zone, that shows evidence that the dead zone itself is rifting further anf further southwards towards the ocean.

Also the propagating rift will eventually, in the far future, extend from the dead zone towards the West Islands and towards Reykjanes. A part of it could also develop as fracture zones, just like it happens nowadays across the SISZ.

Towards the northeast, there are other volcanic systems that could develop further. Kverfjoll is northeast of Grimsvotn, and Esjufjoll is northeast of Oraefajokull, and then Snaefell is further northeast.

I dont think the hotspot moves faster, I think it pushes the jumping of the MAR along its movement. There is a clear track of hotspot centers along Snaefellsnes, Langjokull, Hofsjokull, Bardarbunga and Grimsvotn. The MAR jumped eastwards several times. It will do it again.

So the fact that Bardarbunga is slowly dying out, is shown by the hard plug. Eventually, it will freeze to death and Grimsvotn and Oraefajokull will be the within the location of the hotspot center, receiving its massive magma influx.

If such a large pool of new magma is visible all across Iceland, as Carl says, then this is further evidence of the hotspot pulse. It must be feeding many of Icelandic volcanoes, so prompting them into a new cycle of activity. I reckon this might be why so many Icelandic volcanoes have increased in seismic activity since the Holuhraun eruption.

“But nearby signals show that the bottom of the caldera is dropping, which is also evidenced by the downward slip angles of the larger (M3.5+) earthquakes.”

Well that’s the heart of the conundrum: IMO say explicitly that the movement has reversed: “the movement on the fault is opposite to what it was during the subsidence period during the Holuhraun eruption”. So we have two different interpretation of the data.

It certainly *did* subside initially. My IMO contact wrote to me in Dec. 2014: “The interpretation of the seismicity is that it’s occurring due to continued subsidence of the caldera floor. Since mid August, over 70 earthquakes equal to or greater than Mw 5 have occurred within Bárðarbunga. The focal solutions of these earthquakes show a non-double-couple faulting mechanism, which is best accounted for by ring-faulting associated with caldera collapse.” but evidently they’re seeing something different in the data now.

The next step is obvious: I’ll approach my IMO contact for clarification!

Yes they are, and that is the deep reservoir refilling. There are no contradictions here. The lower magma reservoir is rapidly refilling, but the upper magma reservoir is still depleted. This creates uplift signals at the same time as the plug continues to drop.
I do not think I can write it any clearer than that 🙂

As an analogy, the plug is like a person walking down an ‘up’ elevator, moving downwards in relation to the elevator, but gradually being lifted up overall i.e. net inflation (gross inflation minus gross deflation). I hope I’m not talking nonsense there!

Sorry AM, I missed your comment above. Yes, that is exactly what is happening. The dropping plug deforms the area right outside the ringfault pushing it upwards. And outside of that you have the general uplift from the deep reservoir refilling.
Up and down at the same time with the down being done by the piston, but new fuel on the way up from depth. As the piston and the fuel meet we will get a new eruption in the end.

Great Article, with lots of good info.
If I add it all up, from an aviation perspective, a noticeable eruption in Iceland is likely within the near future, giving us 2-3 years, maximum, to get ready.
If one volcano decides to stay dormant, another one will decide to erupt…
Thanks for the insights,
Klaus

That pretty much sums it up Klaus.
It is though important to remember that this is business as usual in Iceland.
It is also good to remember that there are about 30 other volcanoes that I did not mention that could erupt somewhere in the future.

I would say that the aviation perspective is that aviation was born in one of the more quiet periods of Iceland and it is time for aviation to understand that eruptions will come out of Iceland every 1 to 7 years for the next 40 years.

Only volcano with a well known timer is Grimsvötn. The reason for that being the extremely even rate of magma moving into the magma chambers.
The variations are more stemming from the durability of the part that finally cracks and let the magma out.
But then, Grimsvötn in and of itself is pretty much a black swan in that respect. A very recurring black swan 🙂

Fimmvörduhals was a bit of a special one. It is unclear what volcano actually erupted there. It could have been a separate intrusion, a tendril intrusion from Godabunga, or a general part of the subsequent Eyjafjallajökull. I avoided that question altogether in my list.

Katla 1999 and 2011 and Bárdarbunga 2011 were most likely hydrothermal events and most likely not true eruptions.

Initially I also linked it to Godabunga but when I had a good view at a plot of depth and quake location, I saw something else.

The main feeder dike was halfway between Eyjafjalljokull and Fimmvorduhals (so quite at a distance from Godabunga). GPSs moved away from that point in the east side of Eyjafjallajokull mountain.

On the events of Katla and Hamarinn 2011, we had significant M3 swarms, flood much larger than usual hydrothermal events, sudden sharp high tremor visible all across Iceland. A small Krafla-like eruption would occur subglacial and would never break the ice cap. Just because a volcano is covered by a ice cap does not mean it only has VEI3+ eruptions. In Iceland, actually, small sized efusive eruptions are the norm. Even prior to Holuhraun, the dike or even the caldera might have erupted such small eruptions.

And the flood at Hamarinn back in 2011 was even larger (it even topped a dam from a lake into another lake), but because of the remote location, it received very little attention.

I also remember two very short-lived explosive phreatic events. One at Kverfjoll and another one at Hofjokull (not sure this one was ever discussed in volcanocafe). The one at Kverfjoll was observed by local hut wardens.

I round to keep from accidentally inferring more precision than is there. Sure, the formula may spit out a gazillion digits, but nothing is that precise when it comes to volcanoes. Hell, your lucky if you can get a volcano to agree on a specific century.

@Irpsit, 16.43 “And the flood at Hamarinn back in 2011 was even larger (it even topped a dam from a lake into another lake), but because of the remote location, it received very little attention.”

In 2013, we camped in the middle of (the erstwhile) Hvitalón, and Leynidalur had completely disappeared as a watercourse (which is fitting, given its name).

Something pretty significant had happened to make these changes occur, and I could well believe that it was that Hamarslón was destroyed by the flood waters and these in turn affected Hvitalón. (This is not to say whether it was a geothermal event or an eruption.)

Thank you for this very interesting article!
In my opinion Askja/Herdubreid is also likely to erupt within the next 10 years or so – there is a lot of activity there. Especially the deep quakes of the intrusion at Herdubreid are continuously showing up on the earthqake-map.

I would like to get a clearer image of the caldera plug of Bardarbunga, so may I ask a a few questions: Is the plug solid like a monolith that is being pushed up and down? Or is it more like a formable, flexible area? Flexible in the sense of not the whole plug goes back up, but only small local areas of it when there is pressure forming beneath?

I would like to believe in the monolith-theory that it behaves like a lid that does follow more or less 1:1 the pressure of the chamber, but I doubt it is that simple. But it would be an awesome and easy way to watch the changes in pressure of this volcano.

Herdubreid is a very interesting area, an eruption there would be a once in a millenium experience and there is actually a good chance that we will get to see it.

You ask so good questions that I do not have an answer, and it would surprise me if anyone had any answers.
But, let us play with the plug theoretically. Even if it was solid it would still bend and flex due to the large size of it. Even in smaller circumstances like when a miner digs out a large cavernous gloryhole (yes, that is a correct term) the roof above it will flex over time, and there will be breakages (blocking).
And if it is a large blocky mound of rocks it would due to size and weight behave like it was a solid mass. It would though be far more prone for magma intrusions upwards, and that we do know that Bardarbunga is not prone to do. Perhaps we have an answer here, that it is mainly solid and that prevents upwards intrusions, but that there are a few areas that is susceptible for upwards intrusions and that those areas are causing the cauldrons Mike mentioned above.

First, thanks for the article Carl, a very helpful summary 🙂 Also for the other comments here.

My “fantasy” image of the Bardarbunga plug is largely solid, with weak spots or cracks that have mainly been filled. Over time, this makes for a progressively weaker “block” or “monolith”. And the sides of this, and the caldera wall, have been ground maintaining a tight fit but one filled with some amount of rubble – probably relatively finely ground with some larger pieces in there too.

It’s shape I don’t have a sense of. I guess it’s vaguely cylindrical ie more or less straight vertical edges. Or maybe the edges of the plug lean in towards the centre? I can’t see it being the opposite, like an inverted pyramid. Or, maybe the edges are vertical but the chamber it is descending into begins to widen at some point? This would all effect the progression of the drop, which has been substantial since the 2014 activity began, and may at some point have less frictional resistance. Thoughts?

solid rock is very strong so does this suggest a plug that falls primarily as a result of extension, which if linear would result in catching at the two edges perpendicular to the extension. This is sort of what we are seeing, no?

So the drop has been 60m or so since before the eruption, and the plug was (is?) about 800m thick/deep. If the sides are leaning inwards even slightly, that’s a HUGE amount of increased pressure on the sides unless in the process of dropping the plug/sides have been worn to allow for that drop.

I’m trying to visualise the plug inside that caldera and how it is still sliding down if the angles of the plug and sides aren’t *almost* vertical.

Dunno. But from your link, they state: “The team found that the earthquake created a 40-kilometer-long swath of surface ruptures along the pre-existing Hinagu-Futagawa fault zone, with horizontal displacements of as much as 2.45 meters and vertical shifts of up to 0.9 meters.”

According to calculations using Wells-Coppersmith, a Mag 7.1 usually yields about 41.02 km of surface rupture (assuming reverse faulting). That the quake rupture can be halted by passing into an area of high ductility, it only stand to reason that rupture can no longer be supported.

Side note, the formula also shows that there should be about 928.97 km² of ruptured fault face and 20 km of down dip rupture width.

I think this is a good link to the Wells-Coppersmith abstract. (it’s not the paper from the other link)

Japan will most likely in the not too distant future get a bit of attention again. Problem is mostly that the bulk of articles is written in Japanese and as far as I know nobody of us is fluent in that language. So sourcing papers to read is hard.

Nice and very useful overview Carl! Your method to estimate the next Hekla eruption is interesting, especially if it turns out it works. Earthquakes are I think in most cases less predictive than inflation, but Hekla may be the case against because of the lack of inflation signals. Bardarbunga shows mixed signals. I was wondering why it had a caldera before the eruption. Where did the magma go before? At some point it must have been a mountain, and something drained the chamber. The explosive eruptions seem to have been too small to explain the caldera so my bet would be that the rift eruptions have over time depleted the shallow magma chambers. The problem may not be the plug, but the leaks.

Thank you Albert!
If the model for Hekla pans out I will be a bit proud 🙂
Bárdarbunga was another one where GPS failed as a predictive tool and earthquakes saved the day. Probably for the same reason since the volcano is stretched in EW direction at the same speed as magma enters the system.
The Bárdarbunga caldera is almost certainly from large effusive eruptions, there is not a single known large explosive eruption from the caldera. The VEI-6 eruption 1477 was extra-caldera.

Yepp, Herdubreid is beautifully sculpted by the last ice age. It has had only one post glacial eruption, a small cone formed out of lapilii, you can see it on the top on the picture.

Bardarbunga showed inflation for the months before the eruption, detected by satellite, I believe, but this may not have been noticed until afterwards. The earthquakes were telling, for you as expert. For others it wasn’t easy to separate the meaningful ones from other rumblings.

It is true Albert that the satellite imagery was giving inflation signals that was missed on the GPSes. The signals was though comparatively weak compared to other eruptions in Iceland like Eyjafjallajökull where all of Iceland was visible moving in the weeks prior to the eruption.

The area southwest of Bardarbunga, at Hamarinn, is expericing inflation every year since at least 10 or 15 years. While some of it might be glacial uplifting, a part could have been linked to the magmatic pressure at Bardarbunga.

At Bardarbunga caldera and northeast, as far as I know, there were no GPSs prior to Holuhraun so show us any sign. The entire area is glaciated so it is difficult to measure inflation, unless you have some rocky terrain coming out of the ice cap.

Do we know where exactly the vent of the 1477 eruption is, and is it still identifiable? I’m thinking along the lines of the crater left by the 1933 Cerro Azul eruption vent, or maybe Huaynaputina. (non-caldera forming borderline VEI-6 eruption).

1477 eruption at Bardarbunga was some 100km southwest of the caldera. A dike supposedly came from Bardarbunga (like in 2014 eruption) and travelled southwest towards Torfajokull.

Unlike 2014 – when the dike almost reached Askja but erupted shortly before reaching it – in 1477 it reached Torfajokull, another volcano, and triggered an eruption there.

From ash layers, an explosive rhyolite eruption could have started first at Torfajokull, but followed by a longer and also explosive (very ashy) eruption along a 50km fissure called Veidivotn, which runs across a plain from a bit southwest of Hamarinn and Torfajokull caldera.

Such dike eruptions are common: seven of them are recorded in the Holocene. Initially they were very large lava floods (efusive) but eventually they dammed a river and built a large area of wetland and lakes, which caused the last eruptions, in 870 and 1477, to be very ashy rather than very efusive.

This fissure had many explosive large craters, the largest of them just towards the end of the dike at Torfajokull. The ash layer is one of the thickest in the past millenia in Iceland.

Mickey definitely has piercing, GFUM is slightly west on the Nunatak.
The ice oozes rather rapidly and covers the eruption in the caldera, most of it will be covered up a year after and after a few years there is no trace at all. Gjálp took a little bit more time since it was outside of the caldera and covered a larger area.

I just came home from La Palma (fantastic volcano trecking) and kept an eye on the seismic activity for a couple of months before and until I left. It looked more or less the same similar all the time. Low amplitude low frequence events going and coming. Maybe just noice from traffik or me walking close to the sensor! 🙂

What I noticed is just after the M4 quake late in May, for a period of time the quake location an depths were in an area we did not see as much activity since the start of the eruption. The change is dramatic.

Quakes from June through July

Then the pattern went back to more shallow quakes on the edge of the plug

Upward trend in deep quakes…. this could indicate that magma is finding a way along the plug or the edge of the plug. Eventually it could erupt.

And I think we CANNOT exclude a larger sized caldera eruption. It was a scenario well expected by the Icelandic authorities in 2014 and 2015.

We were all preparing for it (back then I was living in south Iceland). We were stockpiling food, water, masks, radio equipment and knowing how the catastrophic glacial flood would come down the Thrjosá river. We were expecting a truly massive disaster. The IMO predicted if that would happen, ash accumulation could be above 30cm in the roofs (which would risk collapsing many houses), totally loss of visibility and mobile phone communications, SO2, and a truly massive never-seen glacial flood. It was the stuff of movies.

(There is geological evidence in Iceland for the Bardarbunga massive floods, larger than the Katla ones.)

Probably not related to Kaikoura or its aftermath. Geysers here were badly affected by drilling in the 1960’s and 70’s. They are slowly recovering now but still far from what they should be. So this may be a good sign. On the other hand, if you build you house on the site of an extinct geyser, or where a geyser finds a new exit after the previous one was blocked, you might be slightly unhappy about the upside down shower appearing in your garage.

Thanks for this intriguing analysis once again into the Icelandic depths, as always I read it over a few times to try to soak in the details and paint a picture in my head of what is going on.

There is one statement maybe you could clarify a little for me.

“Over time the amount of M3+ earthquakes has steadily dropped and over the next few years Bárdarbunga will become ever more quiescent.”

I have made two plots that illustrate what I believe I have seen that shows that the energy released from BB is still on the rise.

First plot is the total energy released from the BB caldera since 1995. I removed the energy from the eruption so as not to blow the scale of the plot out of the water. The energy released during the mid 90’s shoves the trendline sky high but as it trends down, there appears to be a surge peaking in 2008 and dropping down to rise again leading up to the eruption. Of course the trendline would have sloped upwards dramatically if I had not removed the eruption quakes.

The second plot focuses in on the period after the eruption stopped to present

those are nice and interesting – to ignore the eruption did you just ‘delete’ all those quakes at/near that location time stamp from the dataset – or did you leave the ones that were not directly in the main swarm areas ? and whatever method you did pick how (and how much) do you think that skews the data – not trying to being awkward – just actually interested.

Thanks for this, interesting for sure and for me suggests there is more than a simple drop of the plug going on (not saying that is what Carl has said). I suspect the structure of both the plug and the surroundings were significantly affected by the eruption. Namely, it’s likely that weaknesses are there that weren’t there before, greater instability. As to what extent that is the case, and how the pressures “utilise” that, we don’t know.

Are the scales of the activity pre eruption and post eruption the same?

Yepp, what I tried to say is that what is happening is very complicated.
Plug dropping, but at the same time the entire mountain with the surrounding region is uplifting from the bottom up.
I think I will need to make a very ugly picture since I seem to fail to get what I intend to say through by words. 🙂

Hi All. This link isn’t very informative, as there are no direct links to published papers, but it may be that the information here is onto something that will bear further investigation. It advises of research that, prior to the Yellowstone hotspot, there were other significantly larger eruptions along the Snake River track

Quite a few actually… they are what made the Snake River plain. These are generally ignored by people claiming a 600 kyr “schedule”. Taking all of the ‘Large Caldera Event’s’ into play, the repeat interval is closer to 2.83 Myr… but, that’s not scary enough for the TV programs.

Most people also seem to forget about the ~170Ka VEI-7 eruption that created the West Thumb Caldera, and there was also a VEI-6 event about 143Ka too. Then there are the people that claim an even more “precise” 640 Kyr schedule, and forget that that eruption has been re-dated to about 630,000Ka. And the fact there were quite voluminous precursory pre-caldera eruptions before the main event. And that the 2nd Yellowstone Plateau caldera eruption was a VEI-7 and so not technically a “supereruption”. Needless to say there’s a lot more too it than that!

Well, don’t forget that as a “craton” it hasn’t existed as long as some of the older well cemented together craton out there. It’s really just an older well packed version of terrace plastered on the side of the actual ancient core craton of North America.

It’s always showing. I would be worried if there wasn’t any quake activity, not if there was some. This is like being surprised that a river keeps flowing with water. Not trying to be snarky, but sometimes it’s useful to make an analogy as to what is or isn’t normal.

Since I know that Lurking likes Zombies.
The eat on people Zombie-trend started in Florida, but has now spread world wide. Yesterday evening Sweden had its first case. A man turned violent on a parking lot outside a burger joint and smashed some cars. After that he ran into the burger joint, ripped off his clothes, hit a child and then started to munch on assorted customers.
The staff then barreled the Zombie-muncher into the ground and waited for the police.

The police later issued a statement: “The apprehended is probably not entirely normal in the head”.

And the Max Burger Chain issued this statement: “We have won the tastiest burger in Sweden competition for 25 years in a row, why the hell didn’t he just order a burger if he was that hungry”.

Fun fact, Swedish Max company invented the automatic burger teller thingy that MCDonalds is being berated for.
The reason for it is obvious, Max has to pay a minimum salary of 18USD an hour plus shift-add ons making the salary an average of 24USD per hour.

Except that all the evidence shows a living wage increases overall employment and productivity in an economy. ‘The spirit level’ Authors: Kate Pickett, Richard Wilkinson. As a scientist, I’m all for evidence based policy myself, distinct lack of it in any government these days.

It is better to keep the wages up since that drives the economy and that in turn creates a lot of new jobs for those that lost their job to begin with.
And as edmdas wrote, this is evidence based in the Nordic countries and Germany (among others).
If Ordinary Joe or Jane gets surplus money they spend it, if rich arses get more money they tend to hoard it and sit down and please themselves in a pile of it.

With a higher living wage, sost of living goes up, there is a bit of inflation, and a bit of redistribution of money from richer to poorer. But only if the living wage applies to everyone. If there are ways around it (i.e. the ueber business model), it won’t work. In the longer term, a lot of manual jobs will be taken over by robots. I think this will happen regardless of the level of living wage, so you wouldn’t set the living wage based on the cost of robotification. It is important that local authorities sees these changes coming and encourage new business and retraining of work force, rather than stick to traditional employment. Detroit comes to mind as an example of how not to do it.

Also a bit odd to me that they got the officer to make a statement such as that. Here, a defense attorney would take a statement like that and run with it, using it as evidence of mental incompetency on the part of the defendant.

Here it is mandatory for courts to send people who do things like this for a psychiatric evaluation, if found to be nuts he will be getting mandatory treatment in a closed psychiatric ward. And that often ends up as a life sentence if he is looney enough.
If it was drug induced he will go to prisson instead. Prison sentence would be shorter here, something like 2 to 4 years.

And in cases like this you are either howling to the moon bat shit crazy and should get psychiatric care, or you are a drug addict and should go to prison for your crime.

Well, Parker Florida held a special election to replace one of the city council that got busted making a meth purchase.

What struck me as funny, is that local law enforcement were patting themselves on the back on the radio about their bust of a shake-n-bake meth lab. Later, in that same news report, it turned out that the bust was because that location typically did their lab cooking while grilling out in front of their house. The Fire Department (and the PD) wound up there because the whole shebang went up in a ball of fire. Nope, can’t spot it on your normal patrol, got to have a fireball to get your attention.

On the other hand, we had one who built a nuclear reactor in his kitchen.
He was sent off from court with a stern warning about not doing it again.
He went back home and built another one. This time around he was sent to jail.
He also built a generator that was powered on ANFO.

Years ago I was based on TDY in Klamath Falls,Or. One day while waiting for a fire call-from behind Pelican butte
a ball of smoke and flame came up.
the big Navajo that worked the dispatch
desk, Mike, said:”Load 62.” no call yet but he knew where this was going.
well we got out there, and there was this
circle of flame around this cabin or what was left (chimney) . It was a meth lab gone very wrong. The state and Indian
fire crews got there and found these two
Metheads wandering in ragged clothes and singed hair…
Zombies…

Not sure if there’s something wrong with the HVO data, but Mauna Loa appears to have gone completely aseismic this last week?

On another note, it appears the may have been an eruption at Chirinkotan in the Kuriles, but nothing is confirmed, unmentioned by SVERT so far. But Tokyo VAAC is reporting continued detection of a 30,000ft ash cloud in satellite data. Hmm.

I seem to have failed in explaining myself in words in regards of the mechanics of Bárdarbunga.
So, when you can’t explain by using a 1000 words it is time to try the one image approach.
I suck at making images, but this is accurate in principle but not esthetics.

1. Everything is pushed upwards by the increasing pressure in the lower magma reservoir as it inflates.
2. The plug drops due to the magma chamber pressure still being low.
3. The dropping plug raises the pressure in the chamber forcing the caldera wall upwards while the plug forces the caldera walls outwards at the same time. This gives a false reading on the magma chamber as it seems to be inflating while it is still deflating.

This is conforming to earthquake, GPS and ground radar readings. But, apparrantly it is a bit hard to model mentally.

Interestingly enough, and this has started lately. It seems like there are earthquakes along an outer rim that may be the formation of a new distal ring fault. This started in the last couple of weeks.
If we are stupendously lucky we may see a growth of the caldera itself as the rim starts to drop down into the chamber. This is though highly speculative as of now.

Thank you for your answer above and this easy-to-understand graphic.
It supports my guess that the plug can only be pushed in an upwards direction along with the whole volcano itself, as the lower magma chamber inflates. If the upper magma chamber inflates, the pressure most certainly becomes too punctual to lift the plug as a whole. Well before this happens the pressure will find a way through cracks or more flexible areas of the plug. This may cause a local uplift within the plug or along its edges.

However, I am baffled that the dropping plug could cause the caldera walls to rise more than its surroundings! This thought has never crossed my mind so far. The area and the weight would be huge! It seems logical though, just imagine pressing a ballon on the table with your hand.. the edges do rise as well. But this comparison may be too simple.

OR
The lower chamber is doming the surface above (more surface area).
This means something must fracture, in this case a ring above (would work well).
So outside the ring gets bigger.
Hole gets bigger.
Ring stays the same.
Caldera drops into bigger hole.
Even the uptapering circular fracture fits this scenario.

The winetr forecast situation is very interesting this year. Initially all models forecasted a mild winter for Europe, with increased jet stream activity. It seems that the models failed completely this time.

The reason: the polar vertex. Less know is the fact that there are two polar vertexes: one tropospheric and another stratospheric, and the second one unexpectedly moved from the North Pole towards Siberia, which means a weak polar vertex in general and much higher risk of disruption of the jet stream and cold air pushing southwards.

This happened because of unprecedent Arctic melting this year, (2016 was a crazy year globally overall). November has been record as in some days there was event melting of the Arctic Ocean, despite the polar night! Temperatures have been 20°C higher than average! Which is absolutely insane. I have been following the warm anomaly at Svalbard for example. Its pretty astonoshing.

Likewise, displaced cold in Siberia marks some severe cold anomalies there as well. Cold air that could push towards Europe in wintertime. Changes are for some severe cold outbreaks in Europe this winter. Such a disruption of the polar vertex is much earlier than normal.

As said 2016 has been a crazy year climate-wise. Its was not just El Nino and record warmth at the Troposphere. Many changes observed for the first time in Stratospheric winds. While the most powerful president in the planet calls climate change “an invention and conspiracy by the Chinese”

Stunningly beautiful sunsets today and yesterday – bright blue sky, dazzling sun and bright orange glow along the horizon, pink to purple haze from the frost rising on the hills…. And a silvery blue, still sea….

Of course the current temperature in the UK would have been pretty normal for a November frost day before 1998. The past 20 years have been exceptionally mild, and a normal winter would by now feel as incredibly cold. The arctic temperatures truly are strange, though. One model has it as due to a decreasing jet stream strength, caused by the heating (‘warming’ is no longer the right word) of the polar region. This makes it easier for cold air to breach the polar front and move south.

The threat by the Trump team to end climate research by NASA is hugely worrying. To see science denied and censured because it disagrees with your politics is a sad indictment of the new world. When did science become the enemy?

It’s a bit of a relief: London has waited two years for a proper frost. I have tender bedding plants… sorry, had… bedding plants still going strong from 2014. Hopefully it will sort out a bunch of plant pests and diseases that have been building.

I read a paper on Piton de la Fournaise caldera where they found the rim on the caldera underwent a type of rebound after being dragged down with the plug. Is it possible this may be the situation here?

There has been low level quake activity south of the Mammoth Valley caldera in a vertical north-south line around Convict lake (south of the Mammoth-Yosemite airport). just normal signs the Mammoth caldera is not boring geologically

(WP using firefox + addons + 3rd party cookie restrictions has made posting difficult recently till I figured it out)

Found in the dungeons. (Firefox’s revenge?). Further postings should appear without delay

The unnamed volcano right south of “the big bend” in the dyke that lead to the Holuhráun had a couple of deep magmatic earthquakes again. 3 years of pretty steady activity there now. May be something in the future.

That unnamed volcano might be just a new volcano.
I think watching the birth of a new volcano could be easy but perhaps we would not know for sure whether such eruption happening in a spot would be the very first birth of a new volcano.

For example, what if Holuhraun would become a central volcano. One eruption back in 18th century, one now. Eventually the entire thing erupts regularly in same spot and a new central volcano is born. But the process takes time and we would not suspect of it initially.

Grimsnes might be a new volcano system being born. Starting as monogenic cones that eventually form a central volcano.

Surtsey might be also a volcano in formation, but it erupted in a previously submarine mountain formed by former eruptions. Southwest of Surtsey new volcanoes might form but we would not see them as they would be start as small hills under the ocean.

Hekla is also relatively new. In 8000 years it started from nothing until forming one of the tallest mountains in Iceland and most active volcanoes.

Jumping rifts certainly help. As new spots of activity might appear suddently and start new volcanoes.

Holuhráun is not a formative central volcano since it does not have separate magma conduit system. Nor does it seem likely that one will form.
Grrimsnes may form a central volcano if it forms a magma chamber. The edifice is not the important part.
Surtsey is a long way from becoming a central volcano since it lacks a magma reservoir, Heimey on the other hand is a central volcano.

Iceland has quite a few volcanoes, I guess 50-100? Average life expectancy of a volcano in Iceland is probably not that long. 30,000 yr? A new volcano should appear once every ~500 yr. Once per millennium may be a better guess. Another question is, which are the dying ones? They should get killed at the same rate. The mystery of the murder of an Icelandic volcano – one for Miss Marple. I can see a Carl post coming..

Current number with aquatic volcanoes are about 50 volcanoes that are counted as active in Iceland. So, about one new every 600 years. Problem is that there has only been 5 new volcanoes born in the holocen. Those are Fremrinamur, Heimaey, Heidarspordar, Hekla and Theistareykjarbunga.
Age is a fun thing, the closer the volcanoes are to the central spread axis the older they become, if one would be exactly centered on the spread axis it could probably become immortal almost. It would probably also be the line for new volcanoes forming.
The volcanoes on the central axis are Heimaey, Eyjafjallajökull (oldest volcano in Iceland, 250 000 years old), Torfajökull (on the way to fall off the line) Thordharhyrna, Grimsvötn, Herdubreid, Krafla and Theistarerykjarbunga. All of these except Torfajökull will most likely die in the next ten thousand years, but the rest should be good for att least the next 30 000 years. No other volcano on Iceland will be alive in 30 000 years. Iceland is rearranging itself quite a lot.
The line will probably sprout new volcanoes and Iceland become further extended to the north and the south.

Really good idea for Miss Marple article Albert. I will make a stab at it.

I look forward to the birth of CarlIrpsitVolcanoCafeU-BendaJokull volcano any day now. More seriously, thank you for the steady flow of amazing articles especially around our 5th anniversary. I know from my dire efforts on Ball’s Pyramid that these things take a lot of work to create. So – thank you!

The general trend over the last 100 years has been towards bigger eruptions. But there has been smaller eruptions intermingled with bigger.ones.
In the end it also depends on which magma chamber is erupting, and we only have a record for one of them.
In the end it has to do with the amount of magma that can be expelled. For Grimsvötn that limit is very near the 2011 eruption. Somewhere between the size of 2011 and twice that and the entire caldera floor would drop into the magma chamber together with a very large amount of water and we would get an explosive caldera event on the level of a Saksunarvatn Tephra event.

It has been a little calm over at my favorite area so i thought i would share what i have been reading about since i was pushed by of some our favorites on this website. Found a rather large paper but it talks about Mauna Loa and Kilauea in terms and measurements that the HVO uses on its web page. There is a good discussion on the Jun 2007 intrusion and eruption just to the east of Puʻu ʻŌʻō crater. I think this paper would help us understand we are quite a bit away from an event like that today with our current activity.

Oh yeah the lava lake is only around 15 feet from the deck of the crater right now

It has the energy equivalent of 729 big macs, or 500kg of TNT. Or the brisance of 1 ton of water flashed into dry steam (which is what happens in a hydrothermal explosion in a volcano). It is also the same as a minor mining charge going off.

Thanks. Good for us amateur interested to learn the proportions. So M3+ quakes are within the range of water steam explsions. I guess you can identify them also from their wave profile? Conclusion would be that the shallow quakes we have seen in myrdalsjökul the last 6 months can be explained as water steam explosions? Correct?

It is not all that easy to see if the earthquake is caused by pure rock breakage or a steam explosion is causing the rock to break.
Hydrothermally driven earthquakes are always shallow (normally less than 1km and with a maximum of 2km), and the earthquakes here have almost all been shallow. There is also ample secondary evidence since there has been several episodes where water runoff has rapidly increased and changed in conductivity further indicating hydrothermal events as the origin. All put together, there is no evidence for this being anything but hydrothermal events.

Here I would also like to point towards Krakatau, it produced the largest noise in recorded history, and it was produced by a gigantic steam explosion on the megaton scale.

I realize that these are likely phreatic detonations of varying size. But that still doesn’t answer why they have become more prevalent recently. A few months ago, an argument could be made for seasonality that is often displayed at Katla, but now that it’s getting colder, I feel like that window has passed. In some level of fairness, the activity has decreased since then, but it just seems slightly odd how there are so many of these steam eruptions all of the sudden. As you have said Carl, abnormal activity is never a good thing in a volcanic system, and while these don’t point towards magmatic origins, it IS abnormal.

The other thing that has been strange about these is the very fact that they have not been located on any central spots in the caldera. They’ve stretched all over the caldera at this point.

I would understand if there were some changes within the hydrothermal system (which is still quite likely), but you would figure that would occur in one specific area of the 10km caldera, not in a wide variety of locations as we have seen.

I’m wondering the same cbsu05. Summer melt causing an influx of water available for heating is a reasonable call especially given the widespread area but the intensity appears higher than previous years? Has the heat source changed in location/shape/depth? Has there been deformation that allows water to percolate more? Or is this something other than hydro-thermal activity? Plenty to ponder over there. A question however for the more knowledgeable – How long does it take summer melt water to percolate down through systems like Mýrdalsjökull? If the activity is hydro-thermal, then are we seeing this summers melt being heated or a previous seasons?

A memory lane thing for ‘yall. Quite a few months ago, there was what I referred to as a “Hobbit Launch” in NZ. A steam explosion that lofted material to about 6.5 km.

BTW, you can blame me for the burger reference. Smaller quakes can easily be referenced to the food energy in some meals. (FYI, one food calorie = 1 kcal) I came up with it the idea back when people were going #$%#$% over some Icelandic quakes.. which were quite small and not out of the ordinary. And alternate form of measure is the Twinky, but Cheeseburgers are the usual reference that keep the spirit of the joke alive. Once you get up into the tractor trailer loads of hamburgers, then you are beginning to talk about sizable quakes. For point of reference, one BigMac is about 2,300 kJ… or 550 dietary Calories.

As I wrote in an article a few months ago when it was all going on, it is quite possible that there has been tendril intrusions of hotter material. And, one large earthquake causes fractures for new water to enter and you get another hydrothermal event and after a while it just takes off.
All over the place? I think there are 3 places.

So with the hydrothermal events at Rotorua, is it possible that there is an intrusion event going on there? I would imagine this to be the case as I would assume more quake data would show up, but figured I’d ask anyway.

No, not really. This is a region with active geysers and nothing has changed in the underground plumbing. Drilling before 1990 or so had depleted the hot water and stopped much of the activity. After the drilling was ended, the water reservoirs were slowly beginning to be replenished, and now it is getting to the stage where geysing activity is increasing again. But in the mean time the area had become more build-up.

The big news in volcano land this week is the that there has been a small steam (hydrothermal eruption) in Lake Rotorua. Eruptions have been known in this area all through our written history (1830 – present), so it’s not too unusual. The occurrence of steam eruptions has been variable in Rotorua, with many during the exploitation of the geothermal system, however they declined after the bore closure (1987). The last significant one was in 2001. We’ll be keeping a close eye on this latest hydrothermal eruption but, as this is pretty much business as usual for this system, we aren’t too concerned about it. We went down to check out the eruption and it didn’t leave much interesting evidence.

They comment later on local volcanic activity which is very quiet:
… it looks like the volcanoes have continued to ignore the Kaikoura earthquake sequence

There are periodic large quakes along subduction zones such as the Sumatran coast all the time. Megathrust quakes such as what we saw in the Japan Tsunami or Sumatran Tsunami occur at somewhat regular intervals, and compared to most individual volcanoes, probably happen on a more frequent basis. Many megathrusts have recurrance intervals of around 300-600 years (some are longer, some shorter).

The point here, is that when you extrapolate this out over a much longer geological time period, there isn’t that much of a correlation to eruptive events. A volcano that erupts every 3000 years for instance will likely see 5-10+ megathrusts in its lifetime without those having any effect on said volcano.

Now, there is some loose correlation between earthquakes being able to set off volcanoes that are already extremely close to erupting, but those volcanoes were likely going to erupt anyway with or without the megathrust occurring.

As for Sinabung specifically, it started erupting over 6 years after the Boxing day earthquake. It’s highly unlikely the current activity here is related to the Sumatran Megathrust that occurred in 2004.

There are exactly 3 large earthquakes that are strongly correlated to close by eruptions. One in Chile after Valdivia, The other caused the Santa Maria eruption in Guatemala and the third occurred in Kamchatka.

All 3 volcanoes has been deemed to have been very close to erupting, so the difference may have been days at best. Santa Maria may though have had a far larger eruption since the earthquake may have damaged the edifice causing faults in it to appear and that in turn caused the flank collapse and the ensuing VEI-6 eruption.

“The slow-slip events may mean there is an increased risk of a large earthquake (M7.8 or greater) in the lower North Island. Were such a quake to occur it would be likely to cause a large tsunami that would pose a threat to coastal communities in much of the North Island, the Upper South Island, and Chatham Islands.

We’re aware that these messages could be unsettling, and that’s a very normal reaction. What we do want you to take away from this (and this applies to all New Zealanders, all the time) is that now is the time to be proactive and make sure that you’re prepared for an earthquake and tsunami.”

I find it interesting that they have not changed their forecast from a <1% likelihood of this happening. As the article says the science behind slow slip is relatively new, so much is unknown and they really don't understand the mechanics and therefore what could happen. I guess it makes it difficult to input this into their modelling to update their forecast.

However, even so this update feels a little more than "small print" terms and conditions to avoid future litigation should the worse case scenario happen. It goes without saying that at heart their #1 concern is the safety of the population and protecting lives, property and businesses. Is this a gut feeling update to ensure the message gets out?

To be honest, I'm surprised that the likelihood of a further large earthquake is not even at 1%, even without the slow slip factored in. I wonder how low it actually is, 0.9% is quite a difference from 0.01%.

They have indeed picked up on this. The given chance is less than 1% over 30 days. That is actually quite a high limit, higher than the normal one. The subduction quake may be a once-a-millennium event, in which case the chance per month is 0.01%. For the south island quake, it is expected in the next century which gives 0.1% chance per month. They are being cautious and don’t want to be caught out and told ‘should have read volcanocafe…’

Well that’s part of the concern; once-a-millenium may not be far off the mark – but we have oral history (not 100% reliable but useful) going back nearly that far with no hint of such a quake occurring so far as I’ve heard. So we may well be in the middle of a return window and not know it. Or we may not be of course…

I’m glad to see them exercising caution even if it’s scary to hear what they’re saying. Many volcanologists, geologists, or non-science oriented readers of geo-stuff (like the people on this blog) have a strong aversion to fear-mongering, which is somewhat justifiable considering how often media outlets use volcanoes or earthquakes in non-scientific ways to scare people and generate ratings.

But at the same point, it’s better for people to be aware and prepared even if it may scare some. There is a delicate balance between fear-mongering and proper mitigation, where the line is drawn by what is actually reasonable and possible.

For something like Yellowstone, it’s silly and not realistic fear mongering, and even if there was a legitimate large event, there is not much in the way of mitigation that would do much.

On the other hand, you have cities like Managua, Naples, or Kagoshima that are at great risk for a lot of disaster-related events.

I share Mikes feeling of unease about this.
Yes, there is a lot of things unknown about slow slips, but one thing we do know is that they occur in regions around locked parts of faults. And locks tend to fail sooner or later due to mounting stress.

So, personally I am happy that GeoNet has put the risk level at a very high rate like 1% in 30 days. I just hope that the NZeders take it seriously (which I think they will).
Better safe than sorry in this case.

This image is a few years old now, but shows the area of slip and the apparent “locked” area on the subduction zone.

Comment I’ve heard is of course what’s probably obvious, the recent M7.8 (and increase in slow slip) will have increased stress on the locked section. But there’s also been the comment that if it (and the Alpine Fault) were so close to letting rip and on a “hair trigger”, then the combined multitude of M6+ quakes commencing with the M7.8 in Dusky Sound in 2009 might have triggered these events. The fact that they haven’t (yet?) may be a positive sign, at least for the short term. OTOH either could let rip as I’m typing this. The Alpine Fault is a dead certainly to let rip – 10,000 years of paleo evidence suggests that it’s almost “old faithful” and very regular with average return period of ~300 years – but there’s still a rider of +/- 200 years in that – it wouldn’t be “unusual” just “unlikely” that it won’t let rip before 2200.

The scariest thing to me is that with the high probability that the AF will let rip (currently at 30% in the next 50 years), if that triggers a (near) simultaneous event in the locked subduction zone, then NZ has a very major problem. There is paleotsunami evidence around Cook Strait region which appears to correlate with past Alpine Fault ruptures – the Alpine fault itself will not cause (significant) tsunami, and which faults caused those tsunami is unknown.

I’m not quite so concerned about a possible relationship between the AF and a subduction-zone quake; they’re pretty much at opposite ends of the country.

My concern about the current slow-slip event is twofold:

1. Simply the scale. Slow-slip events have occurred at all these areas before – as individual events. This time they’re all slipping simultaneously. This suggests a common and stronger cause.

2. The common cause is evidently the Kaikoura quake. The large displacements there have apparently instigated this slow-slip sequence a very considerable distance – several hundred km at the far end – away. That means a very considerable quantity of elastic strain energy has been ‘transmitted’ ‘through’ or ‘around’ the area that is locked.

We have – to my knowledge – no certain idea when the locked area last moved or what kind of return periods are involved. But the transfer of so much strain around it cannot be good. And the strain is only increasing as the northern and western margin slow-slips continue.

I was down at the kaikoura coast last year and stayed with an amazing couple running a small B&B.
Here a reply:

Hi XXXX
Remember you both well, I am pleased to report that we are ok in fact I wrote a bit of a blurb to send to
Our friends and guests so will add it below, and yes you are right the sea is definitely lower than it was but not to the extent that it is further up the coast.
An extremely unpleasant experience and would not like to have it repeated and luckily we rose up with the rocks at the same time so it could have been worse if that fault line had torn through the main part of town and South Bay. At present the aftershocks have settled so we are keeping fingers crossed that the worse is over however also know that we could have more over the next year.

Our little home business is stuffed for the year as is most of the town so it is very quiet, one or two cafes up and running so the locals who can seem to meet there for a morning coffee, and it is helping to keep us in contact and in good spirits, still a lot of army trucks and civil defence folk around and scientists and geologists about as this has proved to be the worse quake in NZ history and the movement of the land and sea and the fact that several separate faults erupted at the same time at a rate of 3 km a second I think I heard on the radio, is something they wish to study.

A heap of campervans and rental cars parked up at our racecourse awaiting to be driven out when we finally get some roads open, but that could still take a few weeks hopefully we will get down to Christchurch for our annual Christmas dinner with family but not counting on it, even the small aircraft are fully booked so we will just have to hang in there.
Great to hear from you again XX
Regards to you both
XXXX

Hi
thank you so much for your email, pleased to report that we are ok, sorry for such a delay in getting in touch, had to deal with many cancellations and family phone calls etc. and were without phone email etc for first week, we have had no damage to the house or property, thank goodness for that hard limestone rock under us i think. it was an awful night and very frightening and we spent it up on the peninsula hill with the rest of the town and all the poor tourists that were caught up in this.
spent the following night in the car as well, as many after shocks kept us on our toes.

anyway we have all the services back on, limited showers and water usage and that is wonderful after not having any for 10 days or so, it is amazing how much we waste and have had a good reminder of that!
town has taken a major economic hit and it will difficult for some businesses to survive this, we were all set up for a bumper tourist season and that of course is the problem as no access by road yet, some limited access today for a week or so but the contractors have to repair it as well so we are expecting that we will be stuck here for several weeks yet. the farmers are having to dump milk and have problems with dairy sheds being written off and trying to get water to stock, just today there was a photo on the internet of a lamb which was stuck in a large crack in the ground where the fault line errupted. poor little thing had been stuck all this time but had survived.

we now have been uplifted one metre up, which means that we have a new low tide line and more rocks are exposed out in front of the house it also means that sea rise due to global warming will give us another 50 years!! so guess that is one advantage.
the land has risen a massive 4-6 metres to the north of us and the road and rail lines are completely stuffed so we will be without a main highway to Blenheim for at least a year so they say, and the road route possibly will be altered permanently, to the south, well that has been badly damaged but we are hoping that may open before christmas, the only way out is via the inland route but that is causing major problems and is also the only way to get supplies via the army in.

Pleased to report that sea life all ok baby seals ok and at present a ban on crayfishing and paua as those stocks were affected by the seabed uplift.
The whale watch and dolphin boats are stuck in the marina as the tide line is now to low for them to get out and marina is going to be dredged and rock removed asap so that if the road opens then folk can at least have that experience when here. Of course the main issue for a lot of businessess is the fact that
what was once a main thru fare is now not, so dont have the through traffic wanting coffee and food etc. all in all a bit of a disaster.

a number of homes and business are written off and we had two fatalities, however the support of people such as yourselves has been truly overwhelming and we could not have been luckier.
at least the tourists could be flown out within a few days and we have several carparks all over town with even the racecourse acting as a park for abandoned campers and cars so there is still a massive disruption to the town and rest of south island as accommodation is altered and vehicles booked cannot be returned.
our air field will be extended and better roading etc will benefit from all this, so in the long run at least something good will prevail and one towns fall will give rise to anothers boom, and as a bonus we dont have those big trucks on the road for the next year!

Thanks again for all the care and kind thoughts, we intend to hang in there unless we get an offer we cannot refuse!!! and are in good spirits,
last day of spring today and we are having a little rain, good for the garden at least as have been unable to water it.
stay well and our love and regards